US Service Member Killed in Afghanistan

U.S. military officials say an American service member has been killed in Afghanistan's Nangahar province during an operation targeting Islamic State forces.

Pentagon Press Secretary Peter Cook said Tuesday the service member died when an improvised explosive device went off during a patrol with Afghan forces. To the best of his knowledge no other U.S. or Afghans injured in this attack, Cook added.

"We are heartbroken by this loss" said General John Nicholson, adding that the U.S. remains committed to defeating terrorists in Afghanistan.

The Pentagon says an investigation into the incident is underway.

Islamic State launched its regional operations in Afghanistan early last year in about 10 districts of Nangarhar province, but stiff resistance from the rival Taliban and repeated U.S. counterterrorism drone strikes confined them a few districts, according to officials.

IS has declared Afghanistan, Pakistan and parts of Iran as its Khorasan province.